This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Studies from diverse organisms show that distinct interchromosomal interactions are associated with many developmental events. In some cases, these interactions allow regulatory elements to act in trans, modulating the expression of genes encoded on a separate chromosome held in close proximity. Despite recent advances in uncovering such phenomena, our understanding of how a regulatory element chooses to act on another chromosome remains incomplete. In this proposal, we aim to better understand enhancer action in trans using Drosophila melanogaster as a model system. Specifically, we will ascertain the impacts of enhancer identity and genomic position on trans action, with the potential to identify sequences and/or factors that regulate enhancer action in trans. In addition, we will extend our understanding of the evolutionary history of interchromosomal gene regulation by asking whether the capacity of an enhancer to act in trans is conserved through evolution. Through these studies, we aim to understand the parameters governing enhancer action in trans, and to better grasp how the spatial organization of the nucleus impacts enhancer-promoter specificity.